1. Technical Field
The present invention relates to linear guides and, more particularly, to a linear guide having functions of automatic positioning, automatic assembly-error eliminating, and automatic accumulated-error eliminating.
2. Description of Related Art
A conventional roller linear guide, as shown in FIGS. 1, 2 and 3, primarily comprises a rail 10 and a driven body 15 that can move back and forth along the rail 10. Two sides of the driven body 15 are combined with two sides of the rail 10 through a plurality of rollers 16, which assist the driven body 15 in its linear movement with reduced friction as well as reduced noise and which smoothes the linear movement of the driven body 15.
Each of the rollers 16 of the driven body 15 has an integral outer bush 161 where an outer annular groove 162 is formed for receiving a corresponding side of the rail 10.
People who have ordinary skill in the art of linear guides would appreciate that smooth and steady linear movement of the driven body 15 is available only when each roller 16 and the rail 10 are mated with high accurateness. Such high accurateness can significantly raise the manufacturing costs of the rail 10 and the rollers 16. However, even if the rail 10 and the rollers 16 are formed with the anticipated accurateness, when both are later combined together, assembly errors happening therebetween cannot be fully averted, and such assembly errors can accumulate and cause an accumulated assembly error that adversely effect the operation of the linear guide.
To remedy the problems of the assembly errors and the accumulated assembly error, it has been proposed in the prior art to adjust a position of the axle of each roller 16 to make the outer annular groove 162 of its outer bush 161 accurately engage the rail 10, thereby eliminating possible assembly errors. In such a known approach, referring to FIGS. 1 to 3, each roller 16 is inlaid to a respective moving block 12, which is fastened to the driven body 15 by a set screw 13 and a bias screw 14. Therefore, by adjusting the bias screw 14, the moving block 12 can slant with respect to the set screw 13 to shift the axle of the roller 16 and in turn improve the closeness between the moving block 12 and the rail 10. Consequently, the risk of assembly errors can be eliminated.
However, while each roller 16 is adjusted with respect to the rail 10 one by one, the following problems emerge. That is, the closeness between each roller 16 and the rail 10 may not be identical, and a resulted inequality of mating statuses tends to cause partial variation on the structural tension of the driven body 15, leading to deformation of the driven body 15. In addition, the discrepancy of the mating statuses between the rollers 16 and the rail 10 renders a discrepancy on the outer bushes 161 of the rollers 16. Consequently, after a period of use, the assembly errors and accumulated assembly error can become aggravated, and the driven body 15 will be subject to undesirable jolts during its linear movement.
Besides, since the rollers and rail 10 are assembled relying on manual operation without objective adjustment reference, in the event that the rollers 16 and the rail 10 are combined with undue closeness, the friction therebetween is increased and adversely affects the smooth linear movement of the driven body 15. Besides, the undue friction can significantly reduce the service lives of the rollers 16 and the rail 10.